does anyone remember the spirograph? I loved using the one we had as kids. I actually found one at a garage sale and put it away for the kids for later.

technically the spirograph appears to make hypotrochoids and epitrochoids but unless you are anal retentive like me its very similar. my set had a ruler with the gear teeth down the length of it and if you mesh that and one of the wheels and stuck your pen in one of the holes and traveled down the length of the ruler you would have a trochoid curving loop. Voila! Neato huh?